Flap valve



FIG. 1 is a plan vew of a flap valve showing my new design;

FIG. 2 is a side elevation view thereof;

FIG. 3 is a vertical sectional view thereof;

FIG. 4 is a top perspective view of the flap valve with its flap in a closed position; and,

FIG. 5 is a bottom perspective view thereof. 

The ornamental design for a flap valve, as shown and described. 